43 citations · 178 across the 38 of their papers we have counts for
42 papers
Kriging via variably scaled kernels
Gianluca Audone, Francesco Marchetti, Emma Perracchione +1
Classical Gaussian processes and Kriging models are commonly based on stationary kernels, whereby correlations between observations depend exclusively on the relative distance betw…
Greedy techniques for inverse problems
L. Bruni Bruno, P. Massa, E. Perracchione +1
Inverse imaging problems rely on limited and indirect measurements, making reconstruction highly dependent on both regularization and sample locations. We introduce a novel greedy…
Feature Understanding and Sparsity Enhancement via 2-Layered kernel machines (2L-FUSE)
Fabiana Camattari, Sabrina Guastavino, Francesco Marchetti +1
We propose a novel sparsity enhancement strategy for regression tasks, based on learning a data-adaptive kernel metric, i.e., a shape matrix, through 2-Layered kernel machines. The…
Variably Scaled Kernels for the regularized solution of the parametric Fourier imaging problem
Anna Volpara, Alessandro Lupoli, Emma Perracchione
We address the problem of approximating parametric Fourier imaging problems via interpolation/ extrapolation algorithms that impose smoothing constraints across contiguous values o…
A Recipe for Learning Variably Scaled Kernels via Discontinuous Neural Networks
Gianluca Audone, Francesco Della Santa, Emma Perracchione +1
The efficacy of interpolating via Variably Scaled Kernels (VSKs) is known to be dependent on the definition of a proper scaling function, but no numerical recipes to construct it a…
RIS: Regularized Imaging Spectroscopy for STIX on-board Solar Orbiter
Anna Volpara, Alessandro Lupoli, Frank Filbir +3
Imaging spectroscopy, i.e., the generation of spatially resolved count spectra and of cubes of count maps at different energies, is one of the main goals of solar hard X-ray missio…
Forecasting Geoffective Events from Solar Wind Data and Evaluating the Most Predictive Features through Machine Learning Approaches
Sabrina Guastavino, Katsiaryna Bahamazava, Emma Perracchione +8
This study addresses the prediction of geomagnetic disturbances by exploiting machine learning techniques. Specifically, the Long-Short Term Memory recurrent neural network, which…
Greedy feature selection: Classifier-dependent feature selection via greedy methods
Fabiana Camattari, Sabrina Guastavino, Francesco Marchetti +2
The purpose of this study is to introduce a new approach to feature ranking for classification tasks, called in what follows greedy feature selection. In statistical learning, feat…
Identifying synergies between VLBI and STIX imaging
Hendrik Müller, Paolo Massa, Alejandro Mus +2
Reconstructing an image from sparsely sampled Fourier data is an ill-posed inverse problem that occurs in a variety of subjects within science, including the data analysis for Very…
AI-FLARES: Artificial Intelligence for the Analysis of Solar Flares Data
Michele Piana, Federico Benvenuto, Anna Maria Massone +6
AI-FLARES (Artificial Intelligence for the Analysis of Solar Flares Data) is a research project funded by the Agenzia Spaziale Italiana and by the Istituto Nazionale di Astrofisica…
Unbiased CLEAN for STIX in Solar Orbiter
Emma Perracchione, Fabiana Camattari, Anna Volpara +3
Aims: To formulate, implement, and validate a user-independent release of CLEAN for Fourier-based image reconstruction of hard X-rays flaring sources. Methods: CLEAN is an iterativ…
Mapped Variably Scaled Kernels: Applications to Solar Imaging
Francesco Marchetti, Emma Perracchione, Anna Volpara +3
Variably scaled kernels and mapped bases constructed via the so-called fake nodes approach are two different strategies to provide adaptive bases for function interpolation. In thi…
STIX imaging I -- Concept
Paolo Massa, Gordon. J. Hurford, Anna Volpara +17
Aims. To provide a schematic mathematical description of the imaging concept of the Spectrometer/Telescope for Imaging X-rays (STIX) on board Solar Orbiter. The derived model is th…
Data-driven kernel designs for optimized greedy schemes: A machine learning perspective
Tizian Wenzel, Francesco Marchetti, Emma Perracchione
Thanks to their easy implementation via Radial Basis Functions (RBFs), meshfree kernel methods have been proved to be an effective tool for e.g. scattered data interpolation, PDE c…
Interpolation with the polynomial kernels
Giacomo Elefante, Wolfgang Erb, Francesco Marchetti +3
The polynomial kernels are widely used in machine learning and they are one of the default choices to develop kernel-based classification and regression models. However, they are r…
Forward-fitting STIX visibilities
Anna Volpara, Paolo Massa, Emma Perracchione +6
Aima. To determine to what extent the problem of forward fitting visibilities measured by the Spectrometer/Telescope Imaging X-rays (STIX) on-board Solar Orbiter is more challengin…
First hard X-ray imaging results by Solar Orbiter STIX
Paolo Massa, Andrea F. Battaglia, Anna Volpara +15
Context. The Spectrometer/Telescope for Imaging X-rays (STIX) is one of 6 remote sensing instruments on-board Solar Orbiter. It provides hard X-ray imaging spectroscopy of solar fl…
Greedy algorithms for learning via exponential-polynomial splines
Rosanna Campagna, Stefano De Marchi, Emma Perracchione +1
Kernel-based schemes are state-of-the-art techniques for learning by data. In this work we extend some ideas about kernel-based greedy algorithms to exponential-polynomial splines,…
Imaging from STIX visibility amplitudes
Paolo Massa, Emma Perracchione, Sara Garbarino +5
Aims: To provide the first demonstration of STIX Fourier-transform X-ray imaging using semi-calibrated (amplitude-only) visibility data acquired during the Solar Orbiter's cruise p…
Efficient Reduced Basis Algorithm (ERBA) for kernel-based approximation
Francesco Marchetti, Emma Perracchione
The main purpose of this work is the one of providing an efficient scheme for constructing reduced interpolation models for kernel bases. In literature such problem is mainly addre…
STIX X-ray microflare observations during the Solar Orbiter commissioning phase
Andrea Francesco Battaglia, Jonas Saqri, Paolo Massa +34
The Spectrometer/Telescope for Imaging X-rays (STIX) is the HXR instrument onboard Solar Orbiter designed to observe solar flares over a broad range of flare sizes, between 4-150 k…
Data-driven reduced order modeling of environmental hydrodynamics using deep autoencoders and neural ODEs
Sourav Dutta, Peter Rivera-Casillas, Orie M. Cecil +3
Model reduction for fluid flow simulation continues to be of great interest across a number of scientific and engineering fields. In a previous work [arXiv:2104.13962], we explored…
Feature augmentation for the inversion of the Fourier transform with limited data
Emma Perracchione, Anna Maria Massone, Michele Piana
We investigate an interpolation/extrapolation method that, given scattered observations of the Fourier transform, approximates its inverse. The interpolation algorithm takes advant…
Visibility Interpolation in Solar Hard X-ray Imaging: Application to RHESSI and STIX
Emma Perracchione, Paolo Massa, Anna Maria Massone +1
Space telescopes for solar hard X-ray imaging provide observations made of sampled Fourier components of the incoming photon flux. The aim of this study is to design an image recon…